The present invention relates to the protection of interior wall, window, and adjacent floor surfaces in and around a paint spray booth. The manufacture of many goods requires the application of a decorative finish, either for appearance or protection. The application of a decorative finish is usually performed inside an enclosed area or spray booth. Generally, a spray booth encompasses a sealed chamber with a clean air supply and removal system. The item to be painted is placed inside the booth, and application of the paint is accomplished via hand or automatic spray equipment. Due to paint transfer efficiencies of usually 60% at best, a good deal of the sprayed paint becomes entrained in the booth air flow and ultimately is deposited on the interior surfaces and equipment inside the spray booth. This uncured paint "overspray" fouls the walls and floor and is easily tracked outside the paint booth by workers' shoes and equipment. If allowed to accumulate, this overspray limits visibility through windows in the spray booth, reduces airflow in the booth by narrowing the gap in floor grates, and creates unsafe work conditions by making walking surfaces and equipment slippery. This is especially true in the automotive assembly industry where the uncured paint overspray remains wet unless cured via heating.
Dry time of the coating is an important factor. Spray booth cleaning and maintenance in automotive assembly plants is typically done on shifts when the assembly line is not running. Occasionally, application of paint removers and coatings is done in a brief time interval between a first and second production shift. The varying demands of maintenance schedules require a coating to dry within 2 hours and sometimes within 30 minutes or less of application. Usage of waterborne coatings here presents dry time problems due to the dependence of the coating on the evaporative conditions present in the booth (humidity, temperature and air flow). Many chemical masks dry too slow for applications in time constrained maintenance environments. In addition, many chemical masks do not provide a coating with the transparency or clarity required for unhindered viewing through glass windows in spray booths.
The assembly operations performed on a vehicle, component, or assembly having a decorative finish can be detrimental to this finish. It is often necessary to mask portions of said items to prevent damage. In practice, masking decorative finishes is a costly, time and labor intensive process, sometimes involving additional disposal costs for peelable or paper and plastic-type masking products.
It has long been known that removal of said paint overspray by solvent wiping or spraying is a very effective method. But in view of worker safety and the ever increasing regulation of solvent waste disposal and volatile organic compound air emissions, this approach is losing favor in industry.
Various chemical coating solutions have been posed for protecting spray booths from uncured paint overspray. However, such solutions have not often been successful or found extensive use. Some proposed chemical masks are peelable. These coatings suffer from application difficulties with film thickness; if the coating is not applied thick enough, peelability is compromised. Difficulty in peeling the applied coating from complex surfaces, rivets, and seams of paint spray booths has also be experienced.
Other chemical masks require heated, alkaline, and/or high pressure water for removal; three attributes of water not typically available to maintenance crews cleaning spray booths.
Yet another difficulty is the need to add a surface tension-modifying agent to provide wetting and flow to the coating. Use of said agent adds cost to the coating, and if allowed to accumulate in a spray booth water system, can cause several detrimental effects including paint defects and foaming of the paint booth detackification system.
To produce a tacky, plasticized coating, some chemical coatings solutions require the incorporation of glycerin. Although effective, this plasticizer can impart excessive water absorption and higher surface tension. Excessive water absorption can result in sagging or running of the coating, while high surface tension can result in poor wetting and film formation.
Film clarity in both the wet and dry phase of the film is important. Some assembly plants, especially ones having short application and dry times, require a coating which has excellent transparency when wet and dry. Some current coatings products suffer from poor film transparency or clarity, both in the wet and dry phase.
Some of the above concerns effect application of some of the proposed chemical masks on decorative finishes as well. Ease of removal is required of the protective coating if it is to be non-injurious to the decorative finish. Peeling operations or use of an alkaline water wash could have negative impacts on the appearance a fresh-applied decorative finish.
From the above, it is seen that an improved barrier masking composition with excellent wetting, clarity, durability, and cold water rinsability is called for.